From the time in the middle of 2009 when Tom Queally muscled his way into the weighing-room elite with a series of big-race wins, he has been the jockey who does not do pressure. "It's just another horse race," is such a constant quote in his interviews that you could translate it into Latin and call it his family motto, and he delivers it with such practised ease that much of the time, you could almost believe him.

The reality, of course, is that Queally must feel pressure like anyone else. As John Reid, one of the finest jockeys of the 80s and 90s, put it on Monday: "Of course he feels it, because he's human. If he didn't, he'd be stupid, and Tom Queally is certainly not stupid."

Anyone who has talked to Queally knows that to be true. He speaks with a quiet, thoughtful intelligence about the business of racing and riding, into which he was born, the son of a trainer, nearly 27 years ago.

It is his life, and he will know very well as he weighs out for the Qipco Sussex Stakes at Goodwood on Wednesday afternoon that this two-minute contest over a mile of Downland will be the most important race of his career to date.

Queally rides Frankel, the probable favourite for the showpiece event at Glorious Goodwood. It has attracted just four runners but the race is generally expected to develop into an old-fashioned head-to-head with Canford Cliffs, the only horse other than Frankel with a realistic claim to be the best miler in the world. For several weeks, they had been bracketed together in the ante-post betting, but in the last few days, the market has spoken. The money has arrived for Frankel, who is unbeaten in seven starts, always with Queally in the saddle. The punters expect, and now Queally must deliver.

It will be a contest of two horses and two racing brains, Queally versus Richard Hughes, who rides the tricky Goodwood circuit particularly well. In such a small field, the best horse could easily finish second if the rider on top misjudges the pace, settles in the wrong spot, makes his move too early or leaves it too late. A moment of inspiration by Hughes, or panicked miscalculation by Queally, could, in the one-eyed world of the favourite backers, leave Queally branded forever as the man who got Frankel beaten.

What adds extra spice — and pressure — is that last time out at Royal Ascot, Queally dodged that branding iron by a disturbingly narrow margin. In his previous race, the 2,000 Guineas at Newmarket, he had steered Frankel to victory with a devastating frontrunning ride. At Ascot, though, he settled Frankel in the early stages as Rerouted, his pacemaker, set a strong gallop.

What happened next remains a source of bafflement to many who witnessed it. With barely half of the eight furlongs behind them, Queally rousted Frankel, set off in pursuit of Rerouted and was by him before the home turn. No horse born can maintain such an effort for fully half a mile, and Frankel looked horribly tired as he scrambled across the line less than a length to the good from the Aidan O'Brien-trained Zoffany. In a few more strides, he would have been beaten.

Sir Henry Cecil, Frankel's trainer, and Prince Khalid Abdullah, his owner, looked more shocked than delighted afterwards. Queally suggested that it had all been planned, but in the weeks since, he has seemed reluctant to discuss it at all. There are good rides that lose races, and bad rides that win them, and this was one of those.

"Everybody's got an opinion about that ride and I'll keep mine to myself," Reid says diplomatically, "but it was slightly odd to say the least.

"It's going to be a tricky race at Goodwood, there's very few runners and I think a lot of us would like to see Frankel held up, but that might not be the case and I think that he might have to make his own running.

"Goodwood is quite a nice place to do that, and Frankel is a magnificent horse when you see him moving. I've never seen a horse that gets over the ground as easily as him, or covers so much ground with his stride.

"I'd have loved to ride him in a race like this as I loved a frontrunner. Tom just needs to get the fractions right. If he can do nice, even fractions, he'll win."

It sounds simple. Queally just needs to release Frankel's brilliance as smoothly and evenly as possible over the course of the race, and there may be little that even Canford Cliffs can do about it. Hughes will probably be closing at the line, but the race will already be won.

The practice, of course, can be rather more demanding. A second too quick, and Frankel could have nothing left to fight off Canford Cliffs. A second too slow, and he might be swamped by his rival's finishing kick. And in victory, of course, the bulk of the praise will belong to Frankel. Defeat, whatever Queally does, will be blamed on his rider.

There was speculation after Ascot that Queally's job as stable jockey to Cecil might be under threat. A poor ride on Wednesday could be a setback from which his career — which has already brought him 14 Group One victories in little more than two seasons — might never fully recover.

Such are the thoughts and possibilities that will swirl around Queally as he sets out to ride in "just another race". There will be little margin for error, and no second chances, just a horse and his jockey, and more pressure than Queally has ever known before.